This invention relates to a smoking article, and in particular to a smoking article capable of delivering a flavored aerosol.
Although smoking articles such as cigarettes have remained as popular consumer products, various new types of cigarette-type flavor delivery systems have been proposed. For example, as proposed in U.S. Pat. No. 4,079,742 to Rainer et al, tobacco substitutes can provided from a wide variety of treated and untreated plant materials. However, it is believed that various types of tobacco substitutes, such as are provided by the modification of cellulose materials, are not completely satisfactory as a tobacco substitute.
Numerous aerosol generating smoking articles based on heat generation have been proposed. For example, substitute cigarette filler materials such as carbon fibers treated with flavorant are proposed in U.S. Pat. Nos. 3,738,374 to Bennett; 3,943,941 to Boyd; 4,044,777 to Boyd; 4,286,604 to Ehretsmann et al; 4,326,544 to Hardwick et al and British Pat. No. 1,431,045.
Some proposed aerosol generating smoking articles are believed to have used a heat or fuel source in order to produce an aerosol. One of the earliest of these proposed articles is described by Siegel in U.S. Pat. No. 2,907,686. The Siegel reference proposes a cigarette substitute which includes an absorbent carbon fuel, preferably a 2.5 inch (63.5 mm) stick of charcoal, which is burnable to produce hot gases, and a flavoring agent carried by the fuel, which is adapted to be distilled off incident to the production of the hot gases. Siegel also proposes that a separate carrier, such as clay, may be used for the flavoring agent, and that a smoke-forming agent, such as glycerol, may be admixed with the flavoring agent. Siegel's proposed cigarette substitute may be coated with a concentrated sugar solution to provide an impervious coat and to force the hot gases and flavoring agents to flow toward the mouth of the user.
Another smoking article is described by Ellis et al in U.S. Pat. No. 3,258,015. Ellis et al proposes a smoking article which has an outer cylinder of fuel having good smoldering characteristics, preferably fine cut tobacco or reconstituted tobacco, surrounding a metal tube containing tobacco, reconstituted tobacco, or other source of nicotine and water vapor. It is believed that upon smoking, the burning fuel heats the nicotine source material to cause the release of nicotine vapor and potentially aerosol generating material, including water vapor. It is proposed that the vaporized materials are mixed with heated air which enters the open end of the tube. A substantial disadvantage of this article includes the ultimate protrusion of the metal tube as the tobacco fuel is consumed.
In U.S. Pat. No. 3,356,094, Ellis et al disclose a modification of their original design to eliminate the protruding metal tube upon use. The allegedly improved design employed a tube made out of a material, such as certain inorganic salts or an epoxy bonded ceramic, which is disclosed as becoming frangible tube is disclosed as being removable when the smoker eliminates ash from the end of the article. Even though the appearance of this article is very similar to a conventional cigarette, apparently no commercial product ever has been marketed.
Bolt et al, in U.S. Pat. No. 4,340,072, proposes a smoking article having a fuel rod with a central air passageway and a mouthend chamber containing an aerosol forming agent. The fuel rod preferably is a molding or extrusion of reconstituted tobacco and/or tobacco substitute, although the patent also proposes the use of tobacco, a mixture of tobacco substitute material and carbon, or a sodium carboxymethylcellulose (SCMC) and carbon mixture. The aerosol forming agent is proposed to be a nicotine source material, or granules or microcapsules of a flavorant in triacetin or benzyl benzoate. Upon burning during use of the article, air enters the air passage where it is mixed with combustion gases from the burning rod. The flow of these hot gases reportedly ruptures the granules or microcapsules to release the volatile material. This material reportedly forms an aerosol and/or is transferred into the mainstream aerosol. It is believed that the articles of Bolt et al, due in part to the long fuel rod, would produce insufficient aerosol from the aerosol former to be acceptable, especially in the early puffs. The use of microcapsules or granules further would appear to impair aerosol delivery because of the heat needed to rupture the wall material.
U.S. Pat. No. 3,516,417 to Moses proposes a smoking article, with a tobacco fuel, which is essentially identical to the article of Bolt et al, except that Moses proposes a double density plug of tobacco in lieu of the granular or microencapsulated flavorant of Bolt et al. (See FIG. 4, and col. 4 lines 17-35 of the Moses reference.) Similar tobacco-based fuel articles are described in U.S. Pat. No. 4,347,855 to Lanzilotti et al and in U.S. Pat. No. 4,391,285 to Burnett et al. European Patent Application No. 117,355, by Hearn et al, describes similar smoking articles having a pyrolyzed ligno-cellulosic heat source with an axial passageway therein. These articles would be expected to suffer many of the same problems as the articles proposed by Bolt et al.
Steiner, in U.S. Pat. No. 4,474,191, describes "smoking devices" containing an air-intake channel which, except during the lighting of the device, is completely isolated from the combustion chamber by a fire resistant wall. To assist in the lighting of the device, Steiner proposes providing a means for allowing the brief, temporary passage of air between the combustion chamber and the air-intake channel. Steiner's heat conductive wall also serves as a deposition area for nicotine and other volatile or sublimable tobacco simulating substances. In one embodiment (FIGS. 9 and 10), the Steiner device is provided with a hard, heat transmitting envelope. Materials reported to be useful for the envelope include ceramics, graphite, metals, etc. In another embodiment, Steiner envisions the replacement of the tobacco (or other combustible material) fuel source with some purified cellulose-based product in an open cell configuration, mixed with activated charcoal. This material, when impregnated with an aromatic substance, is stated to dispense a smoke-free, tobaccolike aroma.
None of the foregoing types of smoking articles have ever achieved any commercial success, and it is believed that none has ever been widely marketed. The absence of such smoking articles from the marketplace is believed to be due to a variety of reasons, including insufficient aerosol generation, both initially and over the life of the product, poor taste, off-taste due to the thermal degradation of the smoke former and/or flavor agents.
More recently, Sensabaugh et al, in European Patent Application No. 174,645, describe smoking articles having fuel elements, preferably carbonaceous fuel elements, normally in a heat exchange relationship with a substrate bearing an aerosol forming material. Generally, the aerosol forming material includes at least one polyhydric alcohol and volatile flavoring agents and air can be drawn into the article through the fuel element end of the article or through peripheral perforations along the length of the article. During use of the article, the burning fuel element generates heat used in volatilizing the physically separate aerosol forming materials. The aerosol so formed then is drawn into the mouth of the user.
It would seem desirable to provide a smoking article capable of delivering mainstream tobacco smoke having a high level of flavor while simultaneously delivering a low level of pyrolysis and/or combustion derived wet total particulate matter (WTPM).